1. Life histories Diagrams summarize average life history events (usually with 1-year time steps) Result of natural selection –Represent successful ways of allocating limited resources to carry out various functions of living organisms

2. Tradeoffs Size (survival) vs. number of offspring Fecundity vs. adult survival Age at first reproduction Fecundity and growth

3. Figure 10.7 Phenotypic plasticity: Solid line indicates that reaction norms can evolve!

4. Environmental variation in biological conditions Test for phenotypic plasticity by transplanting individuals (similar genotype) to several environments Expose to predators, different resources

5. Membranipora membranacea: bryozoan common in the PNW Modular species: grows by making new feeding units at the edge of the colony. Chemicals released by predatory nudibranchs induce the formation of spines. Spines protect the bryozoan from predation by nudibranchs. Why not have them all the time?

6. Induced defense reduces growth rate

7. Induced defense reduces reproduction

8. Figure 10.11 Time to metamorphosis depends on food availability In this case, both time and size at metamorphosis are affected

9. Phenotypic plasticity Modular organisms can respond to environmental cues and alter the characteristics of new modules Genotype x environment interaction: plasticity itself can adapt

10. Grime’s plant life histories Competitive: Large, fast potential growth rate, early reproduction, vegetative spread Ruderals: high potential growth rate, early reproduction, production is largely seeds, seed bank/ easily spread seeds Stress tolerators: slow growth rate, late reproduction, little energy to seeds

11. Wilson and Tilman 2002 These data show that plant species coexist best at low rates of fertilization, and moderate rates of disturbance in Minnesota prairies. The authors suggest that coexistence is enhanced due to tradeoffs between competitive and colonization abilities.

12. Competitive ability (Rate of nutrient use) Colonization ability (Seed dispersal)

13. Wilson and Tilman 2002 At low disturbance, lots of perennial plants, shrubs At high disturbance, lots of annual plants, easily dispersed But as soil is fertilized, competitive plants become more common throughout disturbance gradient

14. Populations: Distributions/ Life tables Ruesink lecture 4 Biology 356

15. Ecology includes the study of patterns in the distribution and abundance of species Distribution is the spatial arrangement of organisms within a species –What is their total range? –Are there particular habitat associations? –Within a habitat, is the species clumped, random, or more evenly spaced?

16. Total species on earth Historical filter: Which taxa evolve? Physical filter: What is activity space? Biological filter: Effects of other species?

17. Figure 13.5 Three distinct ways that populations are distributed in space

18. Figure 13.7 Aspen: Clumped, random, or evenly spaced?

19. Figure 13.6 Desert shrubs: Clumped, random, or evenly spaced?

20. Figure 13.3 Distribution often depends on the scale of observation. How is this species distributed across its geographic range? How is it distributed within glades? How are individuals distributed within an aggregate?

21. Ecology includes the study of patterns in the distribution and abundance of species Abundance is the number of individuals in a population –Biologically, a population is a group of regularly-interbreeding individuals –Operationally, it is the size of the researcher’s study site

22. On average, every individual produces one successful offspring (replaces itself) This case represents species that have populations in a dynamic steady state –Births equal deaths

23. Figure 14.12 Elephant seals: 1890 = 20; 1970 = 30,000

24. European starling English ivy Scot’s broom Japanese oysters

25. Invasive species Non-indigenous = alien = exotic = introduced = non-native Why (historically) aren’t all species everywhere? Many species evolved in allopatry and have remained isolated by biogeographic barriers

26. Current rates of invasion are orders of magnitude higher than in the past Ruesink et al. 1995 Bioscience Cumulative number of species

27. In the Galapagos, number of alien plant species is closely related to the human population on the islands

28. Invasion pathways Purposeful –Planned releases –Imports Accidental

29. 85% of exotic woody species in the U.S. were introduced for horticulture Purple loosestrife English ivy European buckthorn English holly

30. Costs and benefits Estimated annual cost of invasive species in US = $137 billion based on 50,000 species ($41 B from crop weeds and pests) Estimated annual benefits = crops and livestock Pimentel et al. 2000 Bioscience

31. Population ecology What makes a good invader? Life history traits of successful invaders from first principles High reproductive rate Modular Broad activity space = generalist, not specialist

32. Evidence – freshwater fishes with smaller body size are more likely to invade (shorter time to maturity)

33. Some species increase rapidly Newly-introduced species Species that can “outbreak” Species hunted to low population levels and then protected –But sometimes they do not recover Births exceed deaths

34. Kareiva et al. 2000 Is harvest or hydropower most responsible for the decline of Columbia River Chinook salmon?

35. Smolts migrate to estuary Chinook spend 3-5 years in the ocean before returning Runs in different seasons are genetically distinct Spawn and die Hatcheries Harvest Hydropower Habitat

36. Some species are in decline Most threatened and endangered species Deaths exceed births

37. Ecologists have developed a simple (!) way of summarizing birth and death schedules Follow the fate of one cohort through the lifespan OR Track the birth and death rates of each life stage

38. Survive and grow to 25 tadpoles 100 eggs Survive and grow to 10 young frogs Survive and grow to 5 adult frogs, each of which lays 20 eggs

39. Life table for frog example Age (x) Number alive Survivorship (l x ) Mortality rate (m x ) Survival rate (s x ) Fecundity (b x ) 0100 125 210 35

40. Survive and grow to 25 tadpoles 100 eggs Survive and grow to 10 young frogs Survive and grow to 5 adult frogs, each of which lays 20 eggs Survivorship 1.0 0.25 0.1 0.05

41. Life table for frog example Age (x) Number alive Survivorship (l x ) Mortality rate (m x ) Survival rate (s x ) Fecundity (b x ) 01001.0 1250.25 2100.1 350.05

42. Survive and grow to 25 tadpoles 100 eggs Survive and grow to 10 young frogs Survive and grow to 5 adult frogs, each of which lays 20 eggs Mortality rate 0.75 0.6 0.5 ??

43. Life table for frog example Age (x) Number alive Survivorship (l x ) Mortality rate (m x ) Survival rate (s x ) Fecundity (b x ) 01001.00.750.25 1250.250.60.4 2100.10.5 350.05

44. Survive and grow to 25 tadpoles 100 eggs Survive and grow to 10 young frogs Survive and grow to 5 adult frogs, each of which lays 20 eggs Fecundity 0 20

45. Life table for frog example Age (x) Number alive Survivorship (l x ) Mortality rate (m x ) Survival rate (s x ) Fecundity (b x ) 01001.00.750.250 1250.250.60.40 2100.10.5 0 350.0520

46. Compare to life history diagram 0123 0.25 0.40.5 20 Differences: Time steps need not be one year. All individuals move from current stage to the next.

47. Life tables x = age l x = survivorship up to age x (proportion living) m x = mortality between age x and age x+1 s x = survival rate from age x to age x+1 b x = fecundity (births) at age x

48. Table 14.4

49. Net reproductive rate R 0 –“R nought” –net reproductive rate, that is, number of offspring produced by average individual R 0 =  l x b x

50. Life table for frog example Age (x) Num ber alive Survivors hip (l x ) Mortality rate (m x ) Survival rate (s x ) Fecundity (b x ) 01001.00.750.250 1250.250.60.40 2100.10.5 0 350.0520 l x b x

51. Life table for frog example Age (x) Num ber alive Survivors hip (l x ) Mortality rate (m x ) Survival rate (s x ) Fecundity (b x ) 01001.00.750.250 1250.250.60.40 2100.10.5 0 350.0520 l x m x 1.0 x 0 = 0 0.25 x 0 = 0 0.1 x 0 = 0 0.05 x 20 = 1

52. Net reproductive rate Note that R 0 does not explicitly determine population growth rate, which depends on both how many and when offspring are produced –Offspring produced earlier lead to higher population growth Need to include average age at which an individual gives birth (generation time)

53. Life table calculations R 0 =Net reproductive rate =  l x b x T = generation time =  x l x b x /  l x b x For frog example, T = (3)(0.05)(20)/((0.05)(20)) = (3)/(1) = 3 These time steps need not be “years”

54. Figure 14.4 Age structure describes the relative contribution of different age classes to total population size

55. Population growth rate and age structure influence each other Age structure can influence population growth

56. Survive and grow to 25 tadpoles 100 eggs Survive and grow to 10 young frogs Adult frogs eaten by horde of herons Total population 135 individuals No reproduction So during this time period the population has to shrink in size. Only mortality occurs.

57. Eggs destroyed by UV radiation Total population 135 individuals 135 x 25/40 = 84 135 x 10/40 = 34 135 x 5/40 = 17 17 x 20 = 340 eggs (compared to 100 from “normal” age structure)

58. Population growth rate and age structure influence each other Population growth rate also influences the age structure of the population

59. Figure 14.8 Population structure also varies for populations with different rates of population growth Births stable since 1950 Births stable since 1990

60. Next week In class assignment on population dynamics We will relate life tables to the exponential and logistic population growth you learned in Bio 180 Bring a calculator!